Extend the search path for the modules which comprise a package. Intended
use is to place the following code in a package’s __init__.py:

frompkgutilimportextend_path__path__=extend_path(__path__,__name__)

This will add to the package’s __path__ all subdirectories of directories
on sys.path named after the package. This is useful if one wants to
distribute different parts of a single logical package as multiple
directories.

It also looks for *.pkg files beginning where * matches the
name argument. This feature is similar to *.pth files (see the
site module for more information), except that it doesn’t special-case
lines starting with import. A *.pkg file is trusted at face
value: apart from checking for duplicates, all entries found in a
*.pkg file are added to the path, regardless of whether they exist
on the filesystem. (This is a feature.)

If the input path is not a list (as is the case for frozen packages) it is
returned unchanged. The input path is not modified; an extended copy is
returned. Items are only appended to the copy at the end.

It is assumed that sys.path is a sequence. Items of sys.path
that are not (Unicode or 8-bit) strings referring to existing directories are
ignored. Unicode items on sys.path that cause errors when used as
filenames may cause this function to raise an exception (in line with
os.path.isdir() behavior).

If dirname is a string, a PEP 302 importer is created that searches that
directory. If dirname is None, a PEP 302 importer is created that
searches the current sys.path, plus any modules that are frozen or
built-in.

If fullname contains dots, path must be the containing package’s
__path__. Returns None if the module cannot be found or imported.
This function uses iter_importers(), and is thus subject to the same
limitations regarding platform-specific special import locations such as the
Windows registry.

If the module or package is accessible via the normal import mechanism, a
wrapper around the relevant part of that machinery is returned. Returns
None if the module cannot be found or imported. If the named module is
not already imported, its containing package (if any) is imported, in order
to establish the package __path__.

This function uses iter_importers(), and is thus subject to the same
limitations regarding platform-specific special import locations such as the
Windows registry.

If fullname contains a “.”, the importers will be for the package containing
fullname, otherwise they will be importers for sys.meta_path,
sys.path, and Python’s « classic » import machinery, in that order. If
the named module is in a package, that package is imported as a side effect
of invoking this function.

Non-PEP 302 mechanisms (e.g. the Windows registry) used by the standard
import machinery to find files in alternative locations are partially
supported, but are searched aftersys.path. Normally, these
locations are searched beforesys.path, preventing sys.path
entries from shadowing them.

For this to cause a visible difference in behaviour, there must be a module
or package name that is accessible via both sys.path and one of the
non-PEP 302 file system mechanisms. In this case, the emulation will find
the former version, while the builtin import mechanism will find the latter.

Items of the following types can be affected by this discrepancy:
imp.C_EXTENSION, imp.PY_SOURCE, imp.PY_COMPILED,
imp.PKG_DIRECTORY.

Yields (module_loader,name,ispkg) for all modules recursively on
path, or, if path is None, all accessible modules.

path should be either None or a list of paths to look for modules in.

prefix is a string to output on the front of every module name on output.

Note that this function must import all packages (not all modules!) on
the given path, in order to access the __path__ attribute to find
submodules.

onerror is a function which gets called with one argument (the name of the
package which was being imported) if any exception occurs while trying to
import a package. If no onerror function is supplied, ImportErrors
are caught and ignored, while all other exceptions are propagated,
terminating the search.

Exemples :

# list all modules python can accesswalk_packages()# list all submodules of ctypeswalk_packages(ctypes.__path__,ctypes.__name__+'.')

This is a wrapper for the PEP 302 loader get_data() API. The
package argument should be the name of a package, in standard module format
(foo.bar). The resource argument should be in the form of a relative
filename, using / as the path separator. The parent directory name
.. is not allowed, and nor is a rooted name (starting with a /).

The function returns a binary string that is the contents of the specified
resource.

For packages located in the filesystem, which have already been imported,
this is the rough equivalent of: